The high speed with which cooking occurs and the broad array of materials suitable for use in microwave ovens has created an ever-increasing demand for economical, simple, disposable containers which, when used in a microwave oven, duplicate as closely as possible the cooking results of a conventional oven. To satisfy the needs of contemporary consumers, such containers must also serve as a shipping carton, display carton and a serving dish. At the same time, it is essential that the container be sufficiently economical to allow it to be disposed after a single use. Paperboard cartons satisfy many of these performance objectives but must be designed in accordance with requirements which are dependent on the type and quantity of food to be placed and cooked in the container. In the case of refrigerated battered food products, a satisfactorily cooked product must have a crisp crust on both sides while avoiding an overcooked, scorched, burned or charred effect. Moreover, the battered food must be heated properly throughout, must not be dry or tough and must be minimally greasy or soggy.
In addition, when refrigerated or frozen battered food products of variable configurations and volumes are to be cooked, such as is the case with chicken legs, wings and breasts, a versatile microwave cooking container is needed which will accommodate a variety of differently sized foods while also applying conductive heat to both sides of the product and allowing controlled drainage and absorption of liquids, such as water and grease, which are released primarily during the latter part of the cooking process.
An important attempt to produce a container to solve many of the problems discussed above is disclosed in the patent to Turpin (U.S. Pat. No. 4,190,757). This patent teaches that, by placing precooked battered food products in a paperboard container having two vertically spaced microwave energy absorbers, such as an interactive layer which converts microwaves into heat, in contact with the food product on its top and bottom, conductive heating will both dry out moisture released by the product during cooking and crisp its top and bottom. However, this container neither provides for disposal through absorption or otherwise of non-evaporable grease released during cooking nor does it produce satisfactory double-sided crisping of variously sized food products without redesign of the carton dimensions. Moreover, the package disclosed in Turpin's patent is complicated and expensive to produce.
The patent to Levinson (U.S. Pat. No. 4,027,132) discloses another effort to overcome some of these problems through a two step method for microwave cooking of frozen filled pies. First, an inverted pie which has been placed onto a water-absorptive material is set on a perforated metal plate and is exposed to microwaves in order to bake its bottom crust and filling. Then the pie is righted into an upright position and further exposed to microwave energy until the raw top pie crust bakes. Throughout this process, a paper pie plate surrounding the pie absorbs shortening released from the crust during baking. However, this patent does not disclose a disposable carton which can be used for both the sale and preparation of refrigerated and frozen battered foods, nor does it disclose a carton which can be used with foods of various sizes to cause crisping of both sides of the food through conductive heating conveyed by a microwave absorptive layer.
The use of any type of microwave reflective or absorptive material in a paperboard carton always presents the possibility of charring or even burning of the food and/or the paperboard material of which the carton is made. Attempts to avoid the danger of charring of the paperboard have normally resulted in the use of an entirely separate element arranged to be placed between the food and the food support or in a complicated outline for the microwave interactive layer which is different from the outline of the paperboard blank on which the interactive layer is supported such as illustrated in the patent to Pothier (U.S. Pat. No. 3,865,301). These prior designs for the microwave interactive layer can add significantly to the cost of the final carton and allow limited flexibility in carton design. Furthermore, it has been discovered that as grease separates from a batter or crust during cooking, it gravitates to the bottom of the container and starts to produce a frying effect which, in turn, creates an adhesion between the crust and the metallized surface on which it rests, making removal difficult, as well as retaining grease on the food product itself. The patent to Winter (U.S. Pat. No. 4,283,427) suggests a solution to the sticking problem by teaching the application of a substantially grease-resistant material to the top of an insert pouch on which a food product would be cooked. Further disclosure concerning stick-resistant coatings is discussed in the patent to Webinger (U.S. Pat. No. 4,279,374), but this reference in no way suggests solutions to the many other problems associated with producing an ideal microwave carton for battered food.
A number of patents have disclosed solutions to some of the specific problems enumerated above, but each has failed to eliminate all of the problems solved by the invention disclosed herein. For example, the patent to Christopher (U.S. Pat. No. 3,411,433) discloses a baking container foil having a bottom layer which absorbs grease and moisture flowing during baking to prevent adhesion, but the foil is not usable in a microwave oven and does not address the problem of crisping both the top and the bottom of a food product. The patent to Woods (U.S. Pat. No. 4,015,085) does disclose a prepackaged structure for use with refrigerated or frozen food designed for exposure to microwaves which also has a moisture absorbent layer on the bottom of the package, but this layer actually prevents crisping of the bottom of the foodstuff since it is not microwave absorbent, and the package makes no provision for crisping the top of a foodstuff. A microwave implement having adjustable shelves which convert microwaves to heat and are placed in contact with opposing sides of a foodstuff to crust both sides thereof is disclosed in the patent to Levinson (U.S. Pat. No. 3,701,872). However, the Levinson patent is not designed for packaging, storage and subsequent sale of refrigerated battered foods, as is the subject of this invention, nor is it an economical, disposable paperboard carton.
Thus, it has remained an elusive goal in the microwave container art to produce a "cook-in" container for refrigerated or frozen battered foodstuffs which is inexpensive, simple to manufacture, disposable, capable of crisping both sides of a product while preventing buildup of grease and flexible enough to handle foodstuffs of various sizes.